Vapreotide acetate is a synthetic analog of somatostatin for the treatment of variceal bleeding; also exhibits antitumor activity.
Somatostatin is a peptide hormone which is distributed in many tissues including the immune system and the nervous system. Vapreotide attenuates the Substance P (SP)-triggered intracellular calcium increases and NF-κB activation in a dose-dependent manner. Vapreotide also inhibits SP-induced IL-8 and MCP-1 production in HEK293-NK1R and U373MG cell lines. Vapreotide inhibits HIV-1 infection of human MDM in vitro, an effect that is reversible by SP pretreatment[1]. Vapreotide significantly inhibits GH-, PRL, and/or alpha-subunit release by human GH-secreting pituitary adenoma cells in concentrations as low as 10-12-10-14 M. Vapreotide inhibits GH release with an IC50 of 0.1 pM[2]. Vapreotide exhibits moderate-to-high affinities for SSTR2, -3, and -5 (IC50=0.17, 0.1 and 21 nM, respectively) and low affinity for SSTR1 and -4 (IC50=200 and 620 nM, respectively). RC-160 inhibits serum-induced proliferation of CHO cells expressing SSTR2 and SSTR5 (EC50=53 and 150 pM, respectively)[3].
In cirrhosis, bleeding by rupture of oesophagogastric varices is a severe complication of portal hypertension. The acute administration of vapreotide to rats decreases collateral circulation blood flow while chronic administration attenuated its development[4]. Tumor volumes and weights are reduced by about 40% by RC-160 by s.c. injections at doses of 100 μg/day/animal. Vapreotide can inhibit the growth of androgen-independent prostate cancer when the therapy is started at an early stage of tumor development[5].
[1]. Spitsin S, et al. Analog of somatostatin vapreotide exhibits biological effects in vitro via interaction with neurokinin-1 receptor. Neuroimmunomodulation. 2013;20(5):247-55. [2]. Hofland LJ, et al. Relative potencies of the somatostatin analogs octreotide, BIM-23014, and RC-160 on theinhibition of hormone release by cultured human endocrine tumor cells and normal rat anterior pituitary cells. Endocrinology. 1994 Jan;134(1):301-6. [3]. Buscail L, et al. Inhibition of cell proliferation by the somatostatin analogue RC-160 is mediated by somatostatin receptor subtypes SSTR2 and SSTR5 through different mechanisms. Proc Natl Acad Sci U S A. 1995 Feb 28;92(5):1580-4. [4]. Veal N, et al. Hemodynamic effects of acute and chronic administration of vapreotide in rats with cirrhosis. Dig Dis Sci. 2003 Jan;48(1):154-61. [5]. Pinski J, et al. Effect of somatostatin analog RC-160 and bombesin/gastrin releasing peptide antagonist RC-3095 on growth of PC-3 human prostate-cancer xenografts in nude mice.